According to the FDA Website:
Decorative contact lenses are sometimes called, among other names:
fashion contact lenses
Halloween contact lenses
color contact lenses
cosmetic contact lenses
theatre contact lenses
For Halloween, many people want to look like they have cat or vampire eyes to go with their costume, or change the color of their eyes to blue or brown. According to the FDA, these contact lenses are medical devices and without advice or purchasing these lenses directly from a doctor…infection may occur. They warn against purchasing these lenses from a beauty supply store or a street vendor.
Dr. Randall Fuerst, chairman of the American Optometric Association's contact lens and cornea section said:
There is no such thing as a 'one-size-fits-all' contact lens. Consumers who purchase lenses illegally, without a prescription or without consultation from an eye doctor, put themselves at risk for serious bacterial infections, allergic reactions or even significant damage to the eye's ability to function, with the potential for irreversible sight loss.
Decorative contact lenses carry the same risks as corrective contact lenses. Because of this, it's important for consumers to obtain a prescription and familiarize themselves with the information available from an eye doctor to reduce the risk of infection.
According to an American Optometric Association survey completed in 2012: 18% of Americans have worn decorative lenses, and 28% bought those lenses without a prescription.